Yasuhiro Hosogi

Hybrid Cu(x)O/TiO₂ nanocomposites as risk-reduction materials in indoor environments.

Photocatalytic TiO(2) powders impart ultraviolet light-induced self-cleaning and antibacterial functions when coated on outdoor building materials. For indoor applications, however, TiO(2) must be modified for visible-light and dark sensitivity. Here we report that the grafting of nanometer-sized Cu(x)O clusters onto TiO(2) generates an excellent risk-reduction material in indoor environments. X-ray absorption near-edge structure using synchrotron radiation and high-resolution transmission electron microscopic analyses revealed that Cu(x)O clusters were composed of Cu(I) and Cu(II) valence states. The Cu(II) species in the Cu(x)O clusters endow TiO(2) with efficient visible-light photooxidation of volatile organic compounds, whereas the Cu(I) species impart antimicrobial properties under dark conditions. By controlling the balance between Cu(I) and Cu(II) in Cu(x)O, efficient decomposition and antipathogenic activity were achieved in the hybrid Cu(x)O/TiO(2) nanocomposites.

Visible light response of AgLi1/3M2/3O2 (M = Ti and Sn) synthesized from layered Li2MO3 using molten AgNO3

AgLi1/3Ti2/3O2 and AgLi1/3Sn2/3O2 with delafossite structures were synthesized by treating the layered compounds Li2TiO3 and Li2SnO3 with molten AgNO3 (573 K for 5 h) through ion exchange of Li+ for Ag+. The band gaps of both AgLi1/3Ti2/3O2 and AgLi1/3Sn2/3O2 were estimated to be 2.7 eV from diffuse reflectance spectra. These delafossite-type metal oxides showed activity for O2 evolution from an aqueous silver nitrate solution under visible light irradiation. Moreover, these materials were also active for photocatalytic degradation of methylene blue under irradiation of monochromatic light at 420 nm. The visible light responses of AgLi1/3Ti2/3O2 and AgLi1/3Sn2/3O2 were due to the band gap excitation between conduction bands consisting of either Ti 3d or Sn 5s5p orbitals and valence bands consisting of Ag 4d orbitals.